1. Field of the Invention
The present invention relates to a communication system, a session control management server and a session control method, and more particularly to a communication system, a session control management server and a session control method for performing a response process in the case of receiving an anonymous call incoming request, with the session control in the internet.
2. Description of the Related Art
At present, with the spread of the internet, an IP telephone service using the internet is provided by each carrier and an Internet Service Provider (ISP). Also, in the IP telephone service, a Voice over IP (VoIP) communication for transferring voice data with an Real Time Transport Protocol (RTP) packet is performed by establishing a channel (session) between the terminals before starting the communication.
As a main session control protocol for making the session establishment and disconnection between the terminals, an Session Initiation Protocol (SIP) is specified for controlling the session between the terminals via an SIP server.
An SIP message is composed of a start line part and a header part for carrying the request or response information and a message body part for describing the session content, in which an Session Description Protocol (SDP), for example, is employed to describe the session content, and the other party of communication is identified by a request Uniform Resource Identifier (URI) described in the start line part. Also, in a process of establishing the session, the RTP packet communication conditions between the terminals, such as calling the receiver, each protocol for voice or video, and the bit rate, are decided.